The effect of liquid-phase sintering on the properties of Pr sub 6 O sub 11 -based ZnO varistors

Journal Article · Sun Dec 01 00:00:00 EST 1991 · Journal of Applied Physics; (United States)

DOI:https://doi.org/10.1063/1.349812· OSTI ID:5155351

Alles, A B; Burdick, V L ^[1]

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1. New York State College of Ceramics at Alfred University, Alfred, New York (USA)

Conventionally batched varistors in the ZnO--Co{sub 3}O{sub 4}--Pr{sub 6}O{sub 11} system that were sintered at or above 1280 {degree}C exhibited a sharp increase in the average breakdown voltage per grain boundary. In these samples, barrier heights and donor concentration values, derived from capacitance-voltage analysis, exhibited sharp changes at the same soaking temperature. At or above 1280 {degree}C, grain growth in this system proceeds with the assistance of an eutectic liquid. The improvement of the distribution of Pr{sub 6}O{sub 11}, by precipitation of Pr(OH){sub 3} during batching, resulted in varistors markedly more insensitive to firing temperature than conventionally batched ones. The presence of a liquid phase, at least during grain growth, results in an efficient distribution of grain boundary materials and dopants in general. Suitable chemisorbed gases along the grain boundaries are believed to be responsible for the formation of interface states. Segregated materials appeared to provide for enhanced transport of gaseous species along the grain boundaries. The need for the addition of oxides with large ionic-radius cations, i.e., varistor-forming oxides such as bismuth, barium, praseodymium, or lanthanum oxide, to varistor compositions is explained within this context.

• OSTI ID: 5155351
• Journal Information: Journal of Applied Physics; (United States), Vol. 70:11; ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ZINC OXIDES
SINTERING
BREAKDOWN
COBALT OXIDES
ELECTRICAL PROPERTIES
GRAIN BOUNDARIES
OVERVOLTAGE
PRASEODYMIUM OXIDES
VAR CONTROL SYSTEMS
VERY HIGH TEMPERATURE
CHALCOGENIDES
COBALT COMPOUNDS
CONTROL SYSTEMS
CRYSTAL STRUCTURE
FABRICATION
MICROSTRUCTURE
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
PRASEODYMIUM COMPOUNDS
RARE EARTH COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
ZINC COMPOUNDS
360204* - Ceramics
Cermets
& Refractories- Physical Properties